WO2007138117A1

WO2007138117A1 - Absorber plate for solar collector, the method for manufacturing it and the solar collector

Info

Publication number: WO2007138117A1
Application number: PCT/ES2006/000283
Authority: WO
Inventors: Claudio Claudemir; Oscar Gonzalez Garcia
Original assignee: Grupo Antolin-Ingenieria, S.A.
Priority date: 2006-05-24
Filing date: 2006-05-24
Publication date: 2007-12-06

Abstract

The absorber plate for a solar collector comprises at least one channel (11) that, when the absorber plate (1) is joined to a closure plate (2), defines a conduit for a heat-transfer fluid. The absorber plate (1) consists of an injection-moulded piece and has at least two through-orifices (14) that place the channel (11) in communication with the outside, at least one perimeter channel (15) for at least one seal, and joining means (16) configured in order to interact with the join between the absorber plate (1) and the closure plate. The invention also relates to a solar collector and to a method for obtaining the absorber plate.

Description

ABSORBER PLATE FOR SOIAR COLLECTOR, ITS MANUFACTURING METHOD, AND SOLAR COLLECTOR

TECHNICAL FIELD OF THE INVENTION The invention is encompassed in the field of solar collectors.

BACKGROUND OF THE INVENTION

Solar collectors typically comprise a housing comprising a cover (usually substantially transparent to solar radiation and often substantially opaque for long-wave thermal radiation, to retain heat inside the housing) and a housing to which the cover is attached . The cover serves to reduce losses by thermal radiation of the collector, and also to reduce heat leakage by conduction and convection. In some cases, a plurality of covers are used. The collectors usually include insulation elements to reduce heat leakage, for example, joints between the cover and the housing.

Inside the housing a device known as an "absorber" is usually housed, since it absorbs the energy of the radiation that falls on it through the cover, transforming it into thermal energy that heats the surface on which the radiation strikes. A heat-carrying fluid flows through the absorber, which heats up as it travels through the absorber. That is, in the absorber, solar radiation (or at least part of it) is transformed into energy thermal, heating the fluid during its passage through the absorber.

Generally, the absorber comprises a series of tubes or, alternatively, two joined plates of which at least one has a configuration that determines one or more channels, which are covered by the other plate, thus defining one or more conduits for the fluid. Many times, one of the plates is flat, and the other is corrugated to define the channels. These plates are often made of metal, although they can also be made of plastic.

DESCRIPTION OF THE INVENTION

A first aspect of the invention relates to an absorber part, or absorber plate, for a solar collector, configured so as to establish at least one channel between at least one input and at least one output (which may correspond to through holes through the plate), so that, when the absorber plate is attached to a closing plate, said, at least one, channel, together with said closing plate, defines at least one fluid conduit between said, at least one, inlet and said, at least one, exit. The channel (or the caneles) travels (n) a greater part of the surface of the absorber plate (for example, 80% or more of said surface), so that said greater part of the surface of the absorber plate is a heat transfer surface to a fluid when said fluid travels through said conduit or conduits. According to the invention, the absorber plate is constituted by an injection molded part, something that can be advantageous compared to many traditional systems, which are based on a union of pipes or the corrugated of an existing plate.

For example, the process of obtaining the plate is simplified, since the complete plate, with its channels and other elements, is obtained from a single material, which can be supplied in bulk, in a single molding phase. By means of the invention, the laborious and expensive union of several components to obtain the absorber plate is avoided. In addition, with a single machine and with a single mold the complete manufacture of the plate is carried out, which minimizes the space occupied in the factory, as well as the number of operations and the necessary machinery. That is, injection molding can be used to optimize the manufacturing process. In addition, using injection molding to make the plates, channels with a reduced cross-section and with a reduced radius of curvature can be obtained. This improves the thermal performance of the absorber plate, since the channels will have a relatively large heat exchange surface compared to the cross-sectional dimensions of the duct. Channels with these reduced dimensions are easily obtainable if the plate is manufactured by injection molding. On the other hand, at least some conventional procedures for obtaining such elements are not compatible with obtaining these reduced dimensions. For example, when using a bent copper tube it can be difficult to have more than approximately 45 channels / linear meter. On the other hand, with the present invention, if a configuration with several parallel channels is chosen (as in Figure 5), 90 can easily be provided channels / linear meter, and with the configuration with a coil channel (as in figure 9) you can easily have 60 channels / linear meter.

In addition, it is easy to prepare custom molds for each application or collector design.

On the other hand, the absorber plate has at least two through holes that communicate the channel or the channels with the outside, to allow an entry and exit, respectively, of a fluid. These holes are obtained directly in the molding process.

On the other hand, the absorber plate additionally has at least one perimeter channel for at least one seal; This channel is also obtained directly in the molding phase, which implies an optimization of the manufacturing process.

On the other hand, the absorber plate additionally has connection means configured to cooperate in the union between said absorber plate and the closing plate; These joining means are also obtained in the molding phase. These means may be sufficient to establish the connection with the closure plate, or be configured to cooperate with other means for attaching the absorber plate to the closure plate.

The ^Xλ at least two "through holes mentioned above may comprise at least four holes, located in correspondence with the corners of the absorber plate. In this way, the possibilities of interconnecting two absorber plates and the possibilities of connecting them to a system are increased. external fluid pumping, something important to have maximum flexibility when designing solar collectors, for example, in cases where the collectors they comprise several interconnected absorber plates so that the fluid travels them according to an established sequence.

The joining means may comprise through holes for screws, clips, turrets for clips, and / or projections and / or recesses configured to fit in the tongue and groove closure plate, or any other method of joining.

The ^λλ at least one channel "mentioned above may comprise a channel that has a coil-shaped path, and that can travel the unseen face of the absorber plate, from one end to another end of said unseen face.

Alternatively, said "at least one channel" may comprise a plurality of parallel or substantially parallel channels, in which case the plate may comprise, along two sides of the plate, two distribution channels, which communicate with said ones, to the minus two, holes and that are interconnected by the other channels (with parallel channels), which can be extended perpendicular to the distribution channels. The distribution channels may be interrupted by partitions that establish a flow path through the parallel channels that join the distribution channels, so that in a plurality of said parallel channels, the fluid will flow in a first direction, and in another plurality of said parallel channels, the fluid will flow in a second direction opposite to said first direction. For example, the partitions can be implemented so that in a consecutive plurality of said parallel channels, the fluid will flow in said first direction, and in another plurality consecutive of said parallel channels, the fluid will flow in said second direction.

The absorber plate may be of a plastic material and / or of a polymeric material, or it may be of metal (for example, of an alloy comprising at least 50% magnesium and / or aluminum).

The channel (or channels) of the absorber plate may have a "semi-cylindrical" configuration, such that the channel establishes a semi-cylindrical conduit once the absorber plate has been coupled to a substantially flat closing plate.

The absorber plate may have an outer face covered by a dark coating comprising carbon fibers or nanofibers that can have an average length greater than or equal to 80 μm and an average diameter greater than or equal to 50 nm and less than or equal to 500 nm, something that can serve to increase the radiation absorbing effect.

Another aspect of the invention relates to a solar collector, which comprises at least one absorber plate according to what has been described above, attached to a first face of a closure plate. The manifold may comprise a plurality of such absorber plates, interconnected so that a fluid can successively pass through the channels of said plurality of absorber plates.

In addition, the manifold may comprise, attached to a second face of said closure plate (or to the second face of several of said closure plates), at least one heat exchange element that establishes a path for a heat carrier fluid in contact with said second face of said closure plate. This Heat exchange element may comprise an absorber plate as described above, which further reduces the number of different parts that have to be used for the complete installation, with the economic and logistical advantages that this implies. The channels of the heat exchange element (or of the heat exchange elements, if there is more than one) can be communicated with an external fluid system without direct connection to the fluid flowing through the channels of the plate or plates absorption, something that allows two independent fluid circuits to be established, with the advantages that this may entail.

The collector may additionally comprise a housing in which said absorber plate (or absorber plates) and the closure plate (and any heat exchange elements) are housed; This housing can be closed by a cover that can be substantially transparent to solar radiation and substantially opaque to thermal radiation, avoiding radiation losses, achieving the commonly called "greenhouse effect".

Another aspect of the invention relates to a method for obtaining an absorber plate according to what has been described above, whose method comprises the step of obtaining said absorber plate from a raw material, by injection molding of said raw material. This allows to obtain the absorber plate, with all its elements and configurations, in a single injection step.

DESCRIPTION OF THE FIGURES To complement the description and in order to help a better understanding of the characteristics of the invention, according to some preferred examples of practical implementation thereof, a set of figures is attached as an integral part of the description in which Illustrative and non-limiting, the following has been represented:

Figure 1 shows a perspective view of a solar collector according to a possible embodiment of the invention.

Figure 2.- Shows an elevation view of said collector, as well as cross sections thereof.

Figure 3.- Shows a detail of the section A-A of figure 2.

Figure 4. - Shows a detail of the B-B section of Figure 2.

Figure 5.- Shows a perspective view of a detail of the unseen (inner) face of the absorber plate according to this preferred embodiment.

Figure 6.- Shows a cross-sectional view of a manifold incorporating a second absorber plate, on the other side of the closure plate.

Figure 7.- Shows a detail of section C-C of figure 2.

Figure 8. - Shows a perspective view of the face of an absorber plate.

Figure 9 shows a perspective view of the unseen face of an absorber plate, according to an alternative embodiment of the invention.

Figure 10.- Shows a plan view of a detail of the absorber plate. PREFERRED EMBODIMENTS OF THE INVENTION

In figure 1 it can be seen how a collector according to a possible embodiment of the invention comprises a housing 5 (in figure 1 the cover is not perceived, since it is transparent), in which absorption devices comprising plates are housed absorbers 1 attached to respective closure plates (which are not seen in Figure 1, since they are attached on the lower surfaces of the absorber plates 1). Each absorber plate 1 comprises four (4) through holes 14, which communicate with one or more channels which, together with the closing plates, define conduits traveled by the heat-carrying fluid. Two of said holes are conveniently closed, while the other two are connected to conduits 18. One of said conduits is a fluid inlet to the manifold, and another is an outlet conduit; The function depends on the direction of the fluid. Another conduit 18 joins two of the absorber plates, so that the fluid entering the solar collector can pass from one absorber plate to another. That is, it is a modular system in which a variable number of absorber plates can be incorporated into the manifold, according to the dimensions of the housing and according to the absorption surface that it is desired to have. This allows to establish collectors of different sizes from absorber plates with a single size. The existence of four holes 14 increases the possibilities of combining and interconnecting the absorber plates in the collector and with the possible external pumping systems of the heat-carrying fluid. In Figure 2 it can be seen how the absorber plates comprise a plurality of joining means 16 configured to cooperate in the connection between the absorber plate 1 and the closing plate; these joining means can, for example, be holes pierced by screws, by means of which the absorber plate is fixed to the closing plate (alternatively, these joining means can comprise clips, turrets for clips, or protruding and / or incoming elements of union by tongue and groove, etc.). The "inlets" 12 and "outlets" 13 of the fluid with respect to each absorber plate have also been schematically illustrated, although, as indicated, each orifice may be inlet or outlet depending on the direction of the fluid. The cover 4 coupled to the housing 5 is also illustrated.

In Figure 3 an enlarged detail of section AA of Figure 2 can be seen, in which the housing 5 and the cover 4 can be seen and, within the housing, the absorber plate 1 and the closing plate 2, constituted by a flat plate. The joining means 16 are constituted by through holes for screws or the like, although it is also possible to use any other suitable joining means. In addition, the joining means present in the absorber plate 1 can be complemented with other means, for example, with welding.

In Figure 3 it can be seen how the absorber plate 1 has a plurality of substantially semi-cylindrical embossments, which extend along most of the surface of the plate 1. These embossments define channels 11 which, together with the plate of closure 2, establish the conduits through which the heat-carrying fluid circulates, which is heated by the absorber plate, which in turn is heated by solar radiation. In figure 3 the throat or perimeter channel 15 can also be seen in which a sealing gasket is housed, for example, of an elastic material.

In Fig. 4 an enlarged detail of the section BB of Fig. 2 is seen. In addition to the aforementioned elements (for example, the perimetral channels 15 running along the unseen faces of the absorber plates 1 in correspondence with their edge), distribution channels 17 are also seen running along the longer sides of the absorber plates (whose configuration is substantially rectangular); • the two distribution channels 17 of each plate are intercommunicated by the channels 11 that extend parallel to each other and that are perpendicular to the distribution channels 17.

These distribution channels can also be seen in Figure 5, which illustrates a part of the unseen face of the plate (in which it can also be seen how, according to a variant of the invention, there are two perimeter channels 15, configured to receive seals together). The through holes 14 flow into these distribution channels 17, which are interrupted by partitions 171 that regulate the flow of the fluid, so that in a first group of adjacent channels 11, the fluid flows in a first direction (illustrated with the arrow 172), to then flow in a second direction (arrow 173) in a next group of adjacent channels 11, etc. In this embodiment, one of the holes 14 illustrated in the figure is closed, and the other represents a fluid inlet 12. On the other hand, it is observed how two channels 11 are separated by a flat part that includes a hole 16 for joining the absorber plate to the closure plate.

As can be seen, the channels 11 have very small dimensions in terms of their cross-section, something that increases the efficiency of heat transfer to the fluid.

Figure 6 schematically illustrates a manifold comprising the housing 5 and cover 4 and, within the housing, the absorber plate 1 (with its channels 11, the perimeter channel 15, the joining means 16, etc.) attached to a first face of the closing plate 2. Furthermore, on the second face of the closing plate, there is a heat exchange element 3, which comprises a plate identical or similar to the heat absorbing plate, and which, more specifically , it also comprises channels 11 through which a fluid can flow. This fluid is heated through the closure plate 2. In this way, a dual fluid system can be provided, that is, two independent circuits: a fluid flows through the absorber plate (s) ), and the other (the one that flows through the channels of the plates or heat exchange devices 3) can leave the outside of the collector and, therefore, be part of a system that takes the heat out of the solar collector. This can be advantageous from a maintenance point of view, and also allows different fluids to be used in the two circuits, something that can be advantageous. Figure 7 reflects an enlarged view detail

CC of Figure 2. It can be seen that in correspondence with the holes 14 there are some highlights annular 141 which serve to couple the tubes 18, which can be made of a flexible and elastic material. In addition, the perimetral channels 15 for the double seal can be observed. Figure 8 illustrates the exposed face of the absorber plate, with its through holes 14 surrounded by the projections 141.

Figure 9 illustrates the unseen face, that is, the face that will be attached on the closure plate, of an absorber plate 1 according to an alternative embodiment of the invention, which does not have the distribution channels 17 but a single channel 11 in the form of a coil, which extends from one of the shortest ends to another of the shortest ends of the plate. In figure 10 it can be seen how the holes 14 communicate with said channel 11 in correspondence with one end of the coil.

The absorber plate 1 is manufactured in a single step and as a "one piece", by injecting a first material into a mold, under pressure (the mold has not been illustrated, since any type of conventional mold can be used, adapted to board configuration). As a raw material, a metal can be used, for example, an aluminum and / or magnesium alloy (for example, alloys with at least 50% of at least one of these metals), or a polymer or plastic. The closing plate can be a simple aluminum sheet.

The absorber plate, according to a preferred embodiment, is covered by a black coating, for example, by a black paint which is conventionally used for this type of applications, but with a carbon nanofiber content (with an average length greater than or equal to 80 μm and with an average diameter greater than or equal to 50 nm and less than or equal to 500 nm), in a proportion of up to 10% by weight.

In this text, the word "comprises" and its variants (such as "understanding", etc.) should not be construed as excluding, that is, they do not exclude the possibility that what is described includes other elements, steps, etc.

On the other hand, the invention is not limited to the specific embodiments that have been described but also covers, for example, the variants that can be made by the average person skilled in the art (for example, in terms of the choice of materials, dimensions , components, configuration, etc.), within what follows from the claims.

Claims

1.- Absorber plate (1) for a solar collector, configured so that it establishes at least one channel (11) between at least one input (12) and at least one output (13), so that, when the absorber plate

(1) is attached to a closure plate, said, at least one, channel (11), together with said closure plate, defines at least one conduit for a fluid between said, at least one, inlet and said, at least one, outlet, said channel (11) running a greater part of the surface of the absorber plate (1), so that said greater part of the surface of the absorber plate (1) is a heat transfer surface to a fluid when said fluid travels said, at least one, duct, characterized in that said absorber plate (1) is constituted by an injection molded part; because said absorber plate (1) has at least two through holes (14) communicating said at least one channel (11) with the outside, to allow an entry and exit, respectively, of a fluid; because said absorber plate (1) additionally has at least one perimeter channel (15) for at least one seal; and because said absorber plate (1) additionally has joining means (16) configured to cooperate in the union between said absorber plate (1) and the closing plate.

2. Absorber plate according to the preceding claim, characterized in that said at least two holes (14) comprise at least four holes (14).

3. Absorber plate according to claim 2, characterized in that said four holes (14) are located in correspondence with the corners of the absorber plate (1).

4. Absorber plate according to any of the preceding claims, characterized in that said joining means (16) comprise through holes for screws.

5. Absorber plate according to any of claims 1-3, characterized in that said joining means (16) comprise clips.

6. Absorber plate according to any of claims 1-3, characterized in that said joining means (16) comprise turrets for clips.

7. - Absorber plate according to any of claims 1-3, characterized in that said joining means (16) comprise projections and / or recesses configured to fit in the tongue and groove closing plate.

8. Absorber plate according to any of the preceding claims, characterized in that said at least one channel (11) comprises a channel that has a coil-shaped path.

9. Absorber plate according to any of claims 1-7, characterized in that said at least one channel (11) comprises a plurality of parallel channels, and because the plate also comprises, along two sides of the plate, two distribution channels (17), which communicate with said at least two holes (14) and which are interconnected by said parallel channels (11).

10. Absorber plate according to claim 9, characterized in that said distribution channels (17) are interrupted by partitions (171) that establish a flow path through the parallel channels (11), so that in a plurality of said parallel channels , the fluid will flow in a first direction (172), and in another plurality of said parallel channels, the fluid will flow in a second direction (173) opposite to said first direction.

11. Absorber plate according to claim 10, characterized in that in a consecutive plurality of said parallel channels (11), the fluid will flow in said first direction (172), and in another consecutive plurality of said channels, the fluid will flow in said second address (173).

12. Absorber plate according to any of the preceding claims, characterized in that it is made of a polymeric material. W 2

18

13. Absorber plate according to any of claims 1-11, characterized in that it is made of metal.

14. Absorber plate according to claim 13, characterized in that it is made of an alloy comprising at least 50% magnesium and / or aluminum.

15. Absorber plate according to any of the preceding claims, characterized in that said at least one channel (11) has a semi-cylindrical configuration.

16. Absorber plate according to any of the preceding claims, characterized in that it has an outer face covered by a dark coating comprising carbon fibers.

17. Absorber plate according to claim 16, characterized in that said carbon fibers have an average length greater than or equal to 80 μm and an average diameter greater than or equal to 50 nm and less than or equal to 500 nm.

18. Solar collector, characterized in that it comprises at least one absorber plate (1) according to any of the preceding claims, attached to a first face of a closure plate (2).

19. Solar collector according to claim 18, characterized in that it comprises a plurality of absorber plates according to any of claims 1-

17, interconnected so that a fluid can pass successively through the channels (11) of said plurality of absorber plates.

20. Solar collector according to claim 18 or 19, characterized in that it also comprises, attached to the second face of said closing plate (2), at least one heat exchange element (3) that establishes a path for a carrier fluid of heat in contact with said second face of said closure plate (2).

21. Solar collector according to claim 20, characterized in that said heat exchange element (3) comprises an absorber plate according to any of claims 1-17.

22. Solar collector according to any of claims 18-21, characterized in that it further comprises a housing (5) in which said absorber plate (1) and said closure plate (2) are housed, said solar collector further comprising at least a cover (4).

23. Method for obtaining an absorber plate according to any of claims 1-17, characterized in that it comprises the step of obtaining said absorber plate from a raw material, by injection molding of said raw material.